FIELD OF THE INVENTION
The invention relates to a low-temperature carbonization/combustion process in which low-temperature carbonization gas generated by a pyrolysis drum is passed into a burner of a combustion chamber, flue gas formed there as a result of combustion is fed through a cooling device and through a gas compressor to an outlet, and pressure in a gas path between the pyrolysis drum and the gas compressor is influenced by the gas compressor. The invention further relates to a low-temperature carbonization/combustion plant which operates according to the process. The process and the plant are used for thermal waste disposal.
The so-called low-temperature carbonization/combustion process has become known in the waste disposal sector. The process and a plant for thermal waste disposal operating in accordance with it are described, for example, in Published European Application No. 0 302 310 A1, corresponding to U.S. Pat. No. 4,878,440, and in German Published, Non-Prosecuted Application DE 38 30 153 A1. The plant for thermal waste disposal according to the low-temperature carbonization/combustion process contains a pyrolysis reactor and a high-temperature combustion chamber as essential components. The pyrolysis reactor converts charged waste into low-temperature carbonization gas and pyrolysis residue. The low-temperature carbonization gas and the pyrolysis residue are then fed to the burner of the high-temperature combustion chamber after suitable treatment. Molten slag is formed in that case, which can be taken off through a discharge and which is present in vitrified form after cooling. The resulting flue gas is fed through a flue gas pipe to a stack as an outlet. A waste heat steam generator acting as a cooling device, a dust filter unit and a flue gas purification plant are preferably installed in the flue gas pipe. Furthermore, situated in the flue gas pipe is a gas compressor which can be disposed directly at the outlet of the flue gas purification plant and can be configured as an induced draught fan. The built-in gas compressor serves for maintaining a reduced, even if slight, pressure in the pyrolysis drum. The reduced pressure prevents low-temperature carbonization gas from escaping through ring seals of the pyrolysis drum to the outside and into the surroundings.
It has been shown that in a low-temperature carbonization/combustion plant, the gas compressor or the induced draught fan can hardly be allowed to run at constant speed of rotation, since as a consequence of varying gas production, a variable pressure in the gas path results between the pyrolysis drum and the gas compressor. Such an inconstant behavior of the gas pressure is undesirable, since in some circumstances, even if only for a short time, it could lead to overshooting or exceeding the ambient pressure and thus to the escape of flue gas, or else to a too intensely reduced pressure in the flue gas path.